Waves in the lower solar atmosphere: the dawn of next-generation solar telescopes

Abstract

Waves and oscillations have been observed in the Sun’s atmosphere for over half a century. While such phenomena have readily been observed across the entire electromagnetic spectrum, spanning radio to gamma-ray sources, the underlying role of waves in the supply of energy to the outermost extremities of the Sun’s corona has yet to be uncovered. Of particular interest is the lower solar atmosphere, including the photosphere and chromosphere, since these regions harbor the footpoints of powerful magnetic flux bundles that are able to guide oscillatory motion upwards from the solar surface. As a result, many of the current- and next-generation ground-based and space-borne observing facilities are focusing their attention on these tenuous layers of the lower solar atmosphere in an attempt to study, at the highest spatial and temporal scales possible, the mechanisms responsible for the generation, propagation, and ultimate dissipation of energetic wave phenomena. Here, we present a two-fold review that is designed to overview both the wave analyses techniques the solar physics community currently have at their disposal, as well as highlight scientific advancements made over the last decade. Importantly, while many ground-breaking studies will address and answer key problems in solar physics, the cutting-edge nature of their investigations will naturally pose yet more outstanding observational and/or theoretical questions that require subsequent follow-up work. This is not only to be expected, but should be embraced as a reminder of the era of rapid discovery we currently find ourselves in. We will highlight these open questions and suggest ways in which the solar physics community can address these in the years and decades to come.

Generation of Vertical Flows by Torsional Alfvén Pulses in Zero-beta Tubes with a Transitional Layer

“…As a result, we should focus on the results for the range ℓ < v A1 τ in order to avoid loss of accuracy of the model. We are able to specify how the pulse is driven via the boundary conditions; in Scalisi et al (2021a), we suggested that a pulse driven for around 150 s could reach a maximum vertical extent matching the height of spicules, and this is within the range of the average period of torsional Alfvén waves in MBPs (where our hypothetical wave driver is located) given by Jess et al (2023). So, for example, if τ = 150 s, along with an estimate of v A1 = 10 km s −1 , we could consider ℓ < 1500 km.…”

“…In this analytical model, beginning with the ideal MHD equations and following on from the method of Scalisi et al (2021a), we consider a magnetic flux tube that acts as a waveguide for an Alfvén wave pulse. In this context, the vertical background magnetic field is assumed to be strong enough that magnetic forces dominate throughout the tube and thus the plasma beta is much less than unity (Jess et al 2023). We therefore use the zero-beta approximation and neglect the plasma pressure in comparison with the magnetic forces.…”

Dissipative Instability of Magnetohydrodynamic Sausage Waves in a Compressional Cylindrical Plasma: Effect of Flow Shear and Viscosity Shear

“…Thus, the smaller the R, the stronger the viscosity. Since m has inverse relation with the radius R, the waves in the small scale flux tube can be more unstable and more easily excited due to the DI in photospheric regions (see, e.g., Section 3.4 in Jess et al 2023), contributing to the enhancement of the wave propagations into the upper atmosphere.…”

Alfvén Wave Connection between the Chromosphere and the Corona of the Sun: An Analytical Study

“…Torsional Alfvén waves were also detected in the photosphere of a pore based on the optical flow detection of angular rotation (Stangalini et al 2021). Some of the key insights into these transverse waves in the solar chromosphere are found in excellent reviews (e.g., Srivastava et al 2021;Jess et al 2023;Morton et al 2023).…”